The Demonic Kind
by MortalAcademy
Summary: It's Halloween at the Institute. Well at least how the Shadowhunters celebrate it anyway, and it's nothing like tradition suggests. In the midst of dancing and enjoying the company of others; a darkness sweeps across the dancefloor and into the hearts, and seeping into the very skin of those there. Nothing can stop this. Nothing can stop Sebastian.


**Prompt:** Hell is empty, all the devils are here.  
><strong>AN:** I was inspired by a prompt from my dear friend Sophia. I took it in my own imagination and made it to my own image.  
><strong>Disclaimer:<strong> I own none of the characters, they belong to the wonderful Cassandra Clare.

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><p>The party had been in full swing for what felt like an eternity, once the music had started and people had began to congregate in the large ballroom that was situated on the ground floor of the New York Insitute, time had effectively stopped. Strobe lights swung in large arcs around the room reflecting off of foil banners and reflective surfaces, along with the bodies that swayed against one another, the lights catching against their bodies casting their dancing twin shadows. A u-shaped table was taking up the furthest wall of the room, a range of different junk foods, exotic cusines and candy were spread over the table top. It was Halloween, the most un-shadowhunter holiday of the year-which was kind of ironic considering their proffesion. Though despite not celebrating, they did break tradition and twist it in their own way, maybe not in the way one would expect.<p>

The bodies of those whom were swaying, gliding, rotating and twisting with one another were not dressed as one should be for a _traditional _Halloween. There was no plastic or rubber masks, there was not stupid or sexy costumes as one would usually see, but the costumes were brilliantly made. Red and black were the only colours, with the effectively flashes of blue and gold throughout the crowd below. Black oil looking costumes were worn by some, others wore a leather looking jaggered costume amongst other things. A blood looking substance, along with a thick black oozing liquid that ran the length of most costumes. It was a definite alternative to what one-a mundane for example-would expect.

Clary watched from the above balcony that ran in a perimeter around the ceiling of the room, looking down on the couples and friends of the Insitute. Isabelle looked completely unlike herself; her hair dishelved slick with the black liquid, while her body was covered in a leather look costume and her face covered the same with her eyes gleaming red. Her brother, Alec was dressed similar, but with his bright blue orbs breaking away the darkness from the room. Magnus had somehow made his costume fitting, though rather stylish-she was rather sure that Isabelle was jealous-he wore a oil looking, leather costume, with red streaked though his black hair. Jace had done the same, looking strangely and frustratingly more attractive than usual. Simon on the other hand stood at her side, in the same as herself. A basic black leather suit, nothing like the ones below. They looked like Shadowhunters, just a little more scary, if that was possible.

The room was filled with he ambience of a party, happiness, friendship and love. Though like even mundanes knew, Shadowhunters knew as well, nothing good lasted forever. The lights swung at sharp angles, she and Simon watched from above while their friends and loved ones danced below. A blow sounding like a bombardment of demolishment balls smashed through the patio doors stretching across the far wall from the buffet table. The razor sharp pieces of glass rained in across the dark mahogany dancefloor, as well as across the array of guests. Nobody should of been able to break through the wards, no demons had been present for a number of months and the piece within Downworld was permanent.

_It was funny how these things happen,_ she thought. _First you believe something is gone for good, then when you see you're doing better, they turn up out of the blue. _That was exactly what happened right now. Clary clenched down on Simon's hand as she took in the scene below, at any other time she would of ran for the nearest weapon or exit, but not this time. It felt her feet were glued to the floor. She watched the gleaming blonde head of hair attatched to a strong, tall body stride through the broken window. Those dark fathomless eyes flickered up, he knew she was there, he always knew. She watched as he ran his tongue across his teeth in sensual manner-which was rather disturbing and sick-grinning at her. She clutched her stomach as she heaved. Nobody's family should make them this sick, but this wasn't family. His was her demonic brother. Sebastian. Jonathan Morgenstern. Murderer of his own kind.

Clary was sinking deeper and deeper into the metal grate on which she was stood, the only thing was keeping her afloat was her parabatai's hand in hers. Her eyes were held and watching every move her brother made, especially when a small black and iron device slid from under his leather sleeve. He was grasping it tightly in his left hand, his fingers curling around the end of the shaft of the device. That was when he spoke.

"Nephilim. Shadowhunters. You are no better than I, I am a stronger and more evolved design. The Angel Raziel should fall to his knees in my present, he is nothing more than a man with wings. I am a man with the power, control and world in the palm of his hands. They say the Shadowhunters are here to protect men, against those who are monsters. You're hypocrites. You cannot protect man from the monsters in the dark when you fratenize with them as _friends_. Downworlders are monsters, parasites a mere experiment between halves.-" Sebastian was looking directly at Magnus and Alec who were stood watching every move her brother made. She could see him glaring down at their interlinked fingers, until Jace stepped into view, folding his arms fiercely across his chest.

"One: You're not welcome here. Two: You are a hypocrite more than anyone. You're biting off remarks about halves when you were no more than an experiment that wasn't wanted. You say we shouldn't be friends with the monster, when you are one. What was it last time we went around this way? You were begging for myself and your sister to join you. Three: You better have some sort of demonic insurance to fix that window." Clary watched as Sebastian smirked, pushing Jace away, both forcefully and meaningfully. Before Jace could react or retort, Sebastian held up a finger.

"Ever the comedian, Jace. Though no you're wrong, I do not want your friendship or loyalty. I'm going to give you what you so call-and by the looks of things want. I am going to make you the very thing you fear the most. You will be the monsters that children fear, mundanes are no wiser about and Shadowhunters kill. I am going to create you in my image. I will use you as a pawn in my game. Prepare for an eternity of darkness, because it's going to shroud you and everything it touches." Clary's eyes widened, realising what he was about to do. She reached up tearing Simon's mask from his face, throwing it as far away as possible. That was when she saw Sebastian press the button on the top of the device.

There was a sharp light that imploded the device and projected a circluar beam of light to all corners of rooms. When it sucked back in, that's when things began to change, costumes began changing, twisting and forming to bodies that wore them. The ooze, blood, leather all came real. Clary stared in horror, glancing from Simon and back to the crowd below. She watched as Jace's hair stayed black and red, while his body twisted to his costume. Then saw Isabelle, Alec and Magnus's costumes do the same. Her and Simon's hands tightened against one anothers in nothing more than fear. They all turned, along with the rest of the crowd glaring up at them, their eyes burning with hunger and hatred. She saw those colours of blue, black and red. She saw her loved ones, her friends and family. They were gone. All that was left was a mess of black and red, monsters.

Glancing down at Sebastian, she watched as he stepped into the fray of the crowd. He fitted in, grinning up at her with a menancing aura about him. They were doomed. One thing that had never happened in all of history was happening now. Demons were in the Insitute.

She knew in that moment; Hell was empty, and all the devils are here.

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><p><strong>Review please, I would really appreciate it :)<strong>


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